Lines Matching refs:power
33 component is "suspended" it is in a nonfunctional low-power state; it
35 "resumed" (returned to a functional full-power state) when the kernel
47 covered to some extent (see Documentation/power/*.txt for more
67 by pressing a power button or opening the cover.
118 We can categorize power management events in two broad classes:
131 The user interface for controlling dynamic PM is located in the power/
133 /sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
143 power/wakeup
154 power/control
172 power/autosuspend_delay_ms
183 Writing "-1" to power/autosuspend_delay_ms and writing "on" to
184 power/control do essentially the same thing -- they both prevent the
188 (In 2.6.21 writing "0" to power/autosuspend would prevent the device
190 power/autosuspend attribute did not exist prior to 2.6.21, and the
191 power/level attribute did not exist prior to 2.6.22. power/control
192 was added in 2.6.34, and power/autosuspend_delay_ms was added in
240 The USB specification states that all USB devices must support power
249 power/control attribute is initialized to "on") for all devices other
290 The requirements for a USB driver to support external power management
404 reason or another. For example, the power/control attribute might be
425 writing "auto" to the device's power/control attribute. Likewise,
430 This is exactly the same as writing "on" to the power/control attribute.
492 Dynamic power management and system power management can interact in
503 Secondly, a dynamic power-management event may occur as a system
518 xHCI host controller provides hardware link power management to usb2.0
521 lower power state(L1 for usb2.0 devices, or U1/U2 for usb3.0 devices),
525 power/ subdirectory of each USB device's sysfs directory, that is, in
526 /sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
529 power/usb2_hardware_lpm
545 controlled link power management, the USB subsystem also has the
546 capability to disable power to ports under some conditions. Power is
550 method calls to set the port power state. For more background see the
556 a shared power well causing power to remain until all ports in the gang
566 goes through during system suspend, i.e. the power session is lost. Any
568 similarly affected by a port power cycle event. For this reason the
572 [1]: http://dl.dropbox.com/u/96820575/sarah-sharp-lpt-port-power-off2-mini.pdf
573 [2]: http://linuxplumbers.ubicast.tv/videos/usb-port-power-off-kerneluserspace-api/
576 power control implementation will block poweroff attempts on that
583 The port power control mechanism uses the PM runtime system. Poweroff is
584 requested by clearing the power/pm_qos_no_power_off flag of the port device
588 This mechanism is dependent on the hub advertising port power switching in its
589 hub descriptor (wHubCharacteristics logical power switching mode field).
600 it will interfere with port power control.
602 Example of the relevant files for port power control. Note, in this example
613 $prefix/3-1:1.0/3-1-port1/power/pm_qos_no_power_off
614 $prefix/3-1:1.0/3-1-port1/device/power/control
637 before their superspeed peer is permitted to power-off. The implication is
639 the port to power-off until its highspeed peer has gone to its runtime suspend
641 guarantee that a superspeed port will power-off.
643 2/ Port resume is sequenced to force a superspeed port to power-on prior to its
647 power session is lost the device may have been removed, or need reset.
648 Resuming the child device when the parent port regains power resolves those
649 states and clamps the maximum port power cycle frequency at the rate the child
652 Sysfs files relevant for port power control:
653 <hubdev-portX>/power/pm_qos_no_power_off:
661 <hubdev-portX>/power/runtime_status:
662 This file reflects whether the port is 'active' (power is on)
705 power is off this port will
711 <child>/power/control:
713 power down until <child>/power/runtime_status
717 <child>/power/persist:
720 power session loss (suspend / port-power event). When
732 echo 0 > power/pm_qos_no_power_off
733 echo 0 > peer/power/pm_qos_no_power_off # if it exists
734 echo auto > power/control # this is the default value
735 echo auto > <child>/power/control
736 echo 1 > <child>/power/persist # this is the default value
745 power/pm_qos_no_power_off set to '1' causing ports to always remain
754 A more aggressive userspace policy is to enable USB port power off for
755 all ports (set <hubdev-portX>/power/pm_qos_no_power_off to '0') when
757 system. For example, a distro may want to enable power off all USB
758 ports when the screen blanks, and re-power them when the screen becomes
759 active. Smart phones and tablets may want to power off USB ports when
760 the user pushes the power button.